Click on the T in the object type palette to select Text mode. Select the pencil tool from the toolbar. Click the mouse where you want to enter the text. A little box with a cursor inside it will appear.
You can make the text box bigger or smaller. Do this by moving the mouse over the bottom right-hand corner of the box. The mouse pointer will change from a pencil to a double-ended arrow at 45 degrees. Click and drag the end of the box to the right and down. Let go of the mouse. Now the box should be a bit bigger. You can change the shape of the text box in this way any time you want to when you are editing text or entering text.
Enter some text by clicking inside the box and typing.